HDMI vs. optical into 2-channel audio

msimmons

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We have a new LG OLED TV that we're streaming on and I want to send the audio to a 2-channel sound system. It's a modern high end tube system (music is my thing) with RCA inputs only. We were streaming from a Roku with sound going to it via optical, with an optical-RCA converter. Now I have the option of sending audio from the LG via HDMI-ARC (which would also have to be converted to RCA) when streaming.

The reasons always given for using HDMI are the sound formats that require greater bandwidth, like 7.1. Not a problem here. So if we're taking sound from the TV and going into 2-channel, is there any difference in sound quality between HDMI-ARC and optical? It looks like they'd be the same signal. In my case, optical would be simpler.

We use an Oppo Blu-Ray for movies we really care about (when available) but stream sometimes, usually for things we don't care as much about, so it's not a huge thing. I do get picky about my sound, though, and with this system I hear all the warts.

P.S. The LG can't stream everything we want (without signing up with them and using a browser for some things) so we're going to keep the Roku. Any difference to be expected in sound or picture between the two? I'm guessing picture is the same but audio processing might be different, maybe in how they down sample to 2 channels, for example.

TIA.
 
The difference here would come from the down grading, if any, from multi channel to 2 channel.
Most tv's are very competent at this these days so you either ask it to send PCM via optical to I presume the Roku (whatever that is) or you plug in the HDMI to the Roku and ask that to do the down grade and digital analogue conversion.
All depends on the quality of the down grading, to know that we need to know which Roku and which LG tv.
From my PS3 I let my Panasonic tv do the down grading for Dolby however it doesn't take on charge DTS so the PS3 does that, as an example. The PCM signal then just passes through a simple DAC (digital analogue converter) so as you can gather I have more confidence in my more modern tv than my PS3 then again it's not a great example.
 
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Sorry if that wasn't clear. I guess there were a few questions mixed in there.

Using the TV as the streaming source, the audio is going from the TV to the stereo audio system's preamp. But the preamp has RCA inputs only so there's a converter inline to go from either optical or HDMI to RCA. The DAC is in the converter but the down sampling would all be done in the TV (PCM). The TV is a 65" LG G2 (OLED65G2PUA). The question is if there will be any difference in quality between using HDMI-ARC or optical from the TV to the 2 channel audio system.

We had previously been using a Roku Ultra 4640X for streaming, sending the video to the TV via HDMI and audio to the stereo via optical. We'll still be using the Roku sometimes. I'm wondering if we'd be better off using the Roku than the LG TV as the streaming device all the time, again sending video to the TV and audio to the sound system. In other words, will the audio from the TV or Roku be better quality? That seems tough to know ahead of time but the TV is new and the Roku is several years old so it sounds like the new TV would probably be better. I might have the cables in place to A-B test that.

Thanks for your help!
 
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No, there will not be any difference just the same digital signal will be sent via either method. I'd use Toslink, optical, to keep the HDMI ARC free for other stuff.
 
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In this application there’s no advantage to using HDMI-ARC, only potential instability (which is always a danger with HDMI-ARC between kit from different manufacturers), so save yourself the hassle and just use optical.
 
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